Watch the video for Just Say No, the Grange Hill single, and there are many things a child would do well to denounce: a mullet, a saxophone solo and wearing a cardigan to a disco. The proper message, though, was an anti-drugs one, taking on first lady Nancy Reagan’s campaign catchphrase, Just Say No. As a result, in what must be the strangest TV/political encounter of all, a number of the Grange Hill cast found themselves invited to the White House in 1986.

Lee MacDonald played Zammo – the character whose heroin addiction provided the hard-hitting storyline – and sat on the sofa next to Mrs Reagan. “We had a little natter,” he says. They talked about the campaign, and he explained the programme to her: “I don’t think she had a clue what Grange Hill was.” It is only looking back, he says, that he realises what a big deal it was, although he did make an effort at the time. “I bought this special suit, but looking at the pictures now, it was awful – the trousers didn’t match and I remember wearing white socks. But I was pleased as punch. We all were. We were really excited. The building is awesome as you walk up. We sat in this room and we heard footsteps coming down the hall, then loads of bodyguards around and then the door opens, and in comes Nancy. It was amazing.”

One of the other cast members who went was Erkan Mustafa, who played Roland “Ro-laaand” Browning. He recalls that it was quite “nerve-racking. I don’t remember much about arriving there, apart from the amount of security. She reached out to shake our hands. She was very welcoming, she was warm. It was interesting to listen to her and what she was doing.”

The visit has given rise to a lurid fable about Mustafa being stoned the entire time he was there – a story that was repeated (with caution) by the Washington Post as recently as 2014. It came from a tabloid sting in 1998 in which Mustafa was said to have boasted about taking a joint to the White House, and claimed to have smoked it in the garden: “When I met Nancy, I was out of it.”

It seems unlikely. Mustafa laughs wearily. “We’re talking about the most protected building in the world, where a president can’t even get a blow job without the rest of the world knowing. How is a 16-year-old kid meant to be doing that? You couldn’t even go for a pee without security. What did I have, the Freedom of the White House?”

It was a story he and some of the other cast members made up after becoming tired of being asked the same questions about it, long after he left the programme. “I came up with a story that bit me on the arse. Looking back, you live and learn.” So the fact that he can’t remember much about the visit wasn’t to do with being high, but a more prosaic reason. “It was 30 years ago!” he says.